1. Field of the Invention
This invention relates to recording head suspensions, and more particularly to improved structures in the load beam and flexure tongue portions of such suspensions, for increased resistance to loss of dimple contact upon lateral shock to the suspension.
2. Related Art
Recording head suspensions comprise a load beam carried by an actuator and a flexure fixed to or integral with the load beam and arranged to carry a slider that incorporates the recording head for travel over a disk having data in tracks. Freedom of movement of the slider in pitch and roll axes is maintained by having a dimple about which the flexure tongue carrying the slider can gimbal. Many factors influence the contact conditions at the dimple location, such as: the preload gram force imposed by the load beam, the flexure vertical and pitch stiffness, the degree of protrusion of the dimple, the forming height of flexure tongue, and friction conditions at the dimple location. For a double dimple contact configuration, see, for example, U.S. Pat. No. 5,666,241 to Summers and U.S. Pat. No. 5,652,684 to Harrison et al, maintaining the alignment of the opposed dimples is difficult given practical manufacturing tolerances, and changes in the Z offset of the suspension may result in non-uniform pitch and roll moments during flying of the assembly.
In the conventional one dimple on a flat surface arrangement, if the slider mass m is heavy and the impact acceleration a is high, a lateral impact force F (shock) tends to be greater than the friction force f at the dimple location. Thus, there is relative slippage between load beam and flexure in the dimple location as the suspension contact factors are overcome by the lateral shock force. This slippage further dampens the sway mode frequency and makes the sway mode response frequency lower.
An increase in the dimple height while presumably increasing the frictional forces f, also produces a high residual stress in the dimple from non-uniform deformation. The limit of dimple height increase is dictated by the metal forming limit; thus the final height of the dimple may be less than required.
It is an object of the invention therefore to provide an improved recording head suspension. It is a further object to provide a recording head suspension with increased resistance to lateral shock. A further object is to define a cooperating dimple and channel structure, one carried by the flexure tongue, the other by the load beam, such that the dimple is blocked on either side by channel walls but free to shift longitudinally, the channel being congruent and close-fitting laterally and larger in extension longitudinally. The dimple then can be in a normal range of radius and still the assembly will resist lateral shock forces dislodging the dimple from the channel.
These and other objects of the invention are realized in a recording head suspension comprising a base portion, a spring portion and a beam portion, a flexure carried by the beam portion, the flexure including a tongue for carrying a slider, the flexure tongue and the load beam portion defining in engaged relation a dimple having substantially the same lateral and longitudinal extension and a dimple retaining structure including a channel laterally congruent with said dimple and having a substantially larger longitudinal extension than the dimple and a lateral extension relative to the dimple lateral extension to closely receive and retain the dimple in laterally blocked but longitudinally free shifting relation, the dimple being blocked from substantial lateral movement and dislodgment from the channel by a lateral shock to the recording head suspension.
In this and like embodiments, typically, the dimple is defined by the flexure tongue and the channel by the beam portion, or vice versa, namely the dimple is defined by the beam portion and the channel by the flexure tongue; the channel has side walls and a bottom wall therebetween, the bottom wall being concave opposite the dimple, whereby the channel is generally cylindrical; the dimple has a given radius, the channel wall being of a larger radius than the dimple such that the dimple radius length is from about 85% to about 98% of a coincident channel radius length, whereby the dimple has rotational freedom within the channel; and the dimple is defined by the flexure tongue and the channel by the beam portion or the dimple is defined by the beam portion and the channel by the flexure tongue.
In a further embodiment, typically, the dimple has a diameter of from 0.01 to 0.025 inch, and is defined by the flexure tongue or the by the beam portion, the channel being defined in either the beam portion or the flexure tongue to be opposite the dimple.